Abrasion resistant sintered copper base cu-ni-sn alloy and bearing made from the same

ABSTRACT

A Cu—Ni—Sn copper-based sintered alloy has a composition including 10 to 40% by mass of Ni, 5 to 25% by mass of Si, and the remainder containing Cu and inevitable impurities, and if necessary, 0.1 to 0.9% by mass of P, 1 to 10% by mass of C, 0.3 to 6% by mass of calcium fluoride or 0.3 to 6% by mass of molybdenum disulfide. In the structure of the alloy, a phase of a composition containing Cu (4-x-y) Ni x Sn y  (where x: 1.7 to 2.3, y: 0.2 to 1.3) is dispersed.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. national phase application under 35 U.S.C. § 371 of International Patent Application No. PCT/JP2007/062841, filed Jun. 27, 2007 and claims the benefit of Japanese Application 2006-176255, filed Jun. 27, 2006. The International Application was published on Jan. 3, 2008 as International Publication No. WO 2008/001789 under PCT Article 21(2) the contents of which are incorporated herein in their entirety.

TECHNICAL FIELD

The present invention relates to a Cu—Ni—Sn copper-based sintered alloy for bearings, having excellent friction properties and wear resistance, and a bearing made of the alloy.

BACKGROUND

A Cu—Ni—Sn copper-based sintered alloy has been used for bearings in the past. Particularly, since the Cu—Ni—Sn copper-based sintered alloy exhibits excellent friction properties and wear resistance in a high-temperature environment, the alloy has been used for, for example, a bearing of a stainless steel reciprocating shaft, which operates the recirculation exhaust gas flow rate control valve of an EGR type internal combustion engine (e.g. see JP-A-2004-68074), or inner and outer rotors of an internal gear pump (e.g. see JP-A-2005-314807), as they are required to have friction properties and wear resistance even in a high-temperature environment.

Moreover, it is known to add a solid lubricant, such as molybdenum disulfide, so as to improve lubricating properties by lowering the friction coefficient of a bearing made of the Cu—Ni—Sn copper-based sintered alloy. The amount of molybdenum disulfide added for improving the lubricating properties of a Cu—Ni—Sn copper-based sintered alloy is generally in the range of 1% to 5%.

SUMMARY OF THE INVENTION

Since the above-mentioned Cu—Ni—Sn copper-based sintered alloy has a relatively large amount of Ni, the alloy has excellent strength, corrosion resistance, friction properties and wear resistance. Particularly, under a high-temperature environment, the alloy exhibits excellent friction properties and wear resistance. However, the alloy needs to be further improved in friction properties and wear resistance.

Therefore, the inventors of the invention studied to improve the friction properties and wear resistance of the above-mentioned Cu—Ni—Sn copper-based sintered alloy. As a result, the inventors have found that friction properties and wear resistance can be improved by forming a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) is dispersed in a matrix of the Cu—Ni—Sn copper-based sintered alloy.

The invention is embodied on the basis of the results of the study.

(1) The invention relates to a Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance, and the alloy has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) is dispersed in a matrix of the Cu—Ni—Sn copper-based sintered alloy containing Ni, Sn and Cu. It is preferable that x is in the range of 1.7 to 2.2 and y is in the range of 0.8 to 1.3.

The Cu—Ni—Sn copper-based sintered alloy containing Ni, Sn and Cu according to (1) may be a Cu—Ni—Sn copper-based sintered alloy which has a composition including 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, and the remainder containing Cu and inevitable impurities, and if necessary, 0.1 to 0.9% by mass of P and/or 1 to 10% by mass of C. When the composition includes 0.1 to 0.9% by mass of P and/or 1 to 10% by mass of C, a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3) and/or a graphite phase are/is produced on the matrix of the Cu—Ni—Sn copper-based sintered alloy.

Accordingly, the invention has the following characteristics.

(2) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) is dispersed in a matrix.

(3) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) and a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3) are dispersed in a matrix.

(4) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 1 to 10% by mass of C and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) and a graphite phase are dispersed in a matrix.

(5) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 1 to 10% by mass of C and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3) and a graphite phase are dispersed in a matrix.

For the ranges described above, Ni is preferably in the range of 15 to 30% by mass, Sn is preferably in the range of 6 to 15% by mass, P is preferably in the range of 0.1 to 0.5% by mass, C is preferably in the range of 3 to 9% by mass, and z is preferably in the range of 0.9 to 1.2.

The Cu—Ni—Sn copper-based sintered alloy containing Ni, Sn and Cu according to any one of (2) to (5) may further include, if necessary, 0.3 to 6% by mass of calcium fluoride. A calcium fluoride phase is dispersed in a matrix of the Cu—Ni—Sn copper-based sintered alloy including the calcium fluoride. Accordingly, the invention has the following characteristics.

(6) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.3 to 6% by mass of calcium fluoride and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) and a calcium fluoride phase are dispersed in a matrix.

(7) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 0.3 to 6% by mass of calcium fluoride and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3) and a calcium fluoride phase are dispersed in a matrix.

(8) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 1 to 10% by mass of C, 0.3 to 6% by mass of calcium fluoride and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a graphite phase and a calcium fluoride phase are dispersed in a matrix.

(9) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 1 to 10% by mass of C, 0.3 to 6% by mass of calcium fluoride and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3), a graphite phase and a calcium fluoride phase are dispersed in a matrix.

For the range described above, calcium fluoride is preferably in the range of 0.5 to 5% by mass.

The Cu—Ni—Sn copper-based sintered alloy containing Ni, Sn and Cu according to any one of (2) to (5) may further include, if necessary, 0.3 to 6% by mass of molybdenum disulfide. A molybdenum disulfide phase is dispersed in a matrix of the Cu—Ni—Sn copper-based sintered alloy including the molybdenum disulfide. Accordingly, the invention has the following characteristics.

(10) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) and a molybdenum disulfide phase are dispersed in a matrix.

(11) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3) and a molybdenum disulfide phase are dispersed in a matrix.

(12) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 1 to 10% by mass of C, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a graphite phase and a molybdenum disulfide phase are dispersed in a matrix.

(13) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 1 to 10% by mass of C, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3), a graphite phase and a molybdenum disulfide phase are dispersed in a matrix.

For the range described above, molybdenum disulfide is preferably in the range of 0.5 to 5% by mass.

The Cu—Ni—Sn copper-based sintered alloy containing Ni, Sn and Cu according to any one of (2) to (5) may further include, if necessary, 0.3 to 6% by mass of calcium fluoride and 0.3 to 6% by mass of molybdenum disulfide. A calcium fluoride phase and a molybdenum disulfide phase are dispersed in a matrix of the Cu—Ni—Sn copper-based sintered alloy including the calcium fluoride and the molybdenum disulfide. Accordingly, the invention has the following characteristics.

(14) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.3 to 6% by mass of calcium fluoride, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a calcium fluoride phase and a molybdenum disulfide phase are dispersed in a matrix.

(15) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 0.3 to 6% by mass of calcium fluoride, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3), a calcium fluoride phase and a molybdenum disulfide phase are dispersed in a matrix.

(16) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 1 to 10% by mass of C, 0.3 to 6% by mass of calcium fluoride, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a graphite phase, a calcium fluoride phase and a molybdenum disulfide phase are dispersed in a matrix.

(17) A Cu—Ni—Sn copper-based sintered alloy having excellent friction properties and wear resistance. The alloy has a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 1 to 10% by mass of C, 0.3 to 6% by mass of calcium fluoride, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and has a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3), a graphite phase, a calcium fluoride phase and a molybdenum disulfide phase are dispersed in a matrix.

For the range described above, calcium fluoride and molybdenum disulfide are preferably in the range of 0.5 to 5% by mass, respectively.

The Cu—Ni—Sn copper-based sintered alloy according to any one of (1) to (17), exhibits excellent friction properties and wear resistance. In addition, the alloy according to the invention exhibits improved friction properties and wear resistance when it is used for various electrical parts and machine parts, and particularly, for oil-impregnated bearings. Particularly, when the alloy according to the invention is used for the bearing of a shaft having a high-rotation frequency, a bearing having a long lifetime is effectively obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pattern diagram showing a structure of a Cu—Ni—Sn copper-based sintered alloy according to the invention, which has excellent friction properties and wear resistance.

FIG. 2 is a pattern diagram showing a structure of the Cu—Ni—Sn copper-based sintered alloy according to the invention, which has excellent friction properties and wear resistance.

FIG. 3 is a pattern diagram showing a structure of the Cu—Ni—Sn copper-based sintered alloy according to the invention, which has excellent friction properties and wear resistance.

FIG. 4 is a pattern diagram showing a structure of the Cu—Ni—Sn copper-based sintered alloy according to the invention, which has excellent friction properties and wear resistance.

FIG. 5 is a pattern diagram showing a structure of the Cu—Ni—Sn copper-based sintered alloy according to the invention, which has excellent friction properties and wear resistance.

FIG. 6A is a plan view showing an example of the embodiment of a bearing made of the Cu—Ni—Sn copper-based sintered alloy according to the invention, which has excellent friction properties and wear resistance.

FIG. 6B is a cross-sectional view showing an example of the embodiment of the bearing made of the Cu—Ni—Sn copper-based sintered alloy according to the invention, which has excellent friction properties and wear resistance.

SUMMARY OF THE INVENTION

To produce the Cu—Ni—Sn copper-based sintered alloy according to any one of the above (1) to (17), having excellent friction properties and wear resistance, the following raw powders are prepared:

a Cu—Ni alloy powder having a composition containing 5 to 45% by mass of Ni and the remainder containing Cu and inevitable impurities;

a Cu—Ni—Sn alloy powder having a composition containing 25 to 60% by mass of Ni, 5 to 60% by mass of Sn and the remainder containing Cu and inevitable impurities;

a Sn powder;

a Cu—P alloy powder having a composition containing 8% by mass of P and the remainder containing Cu and inevitable impurities;

a graphite powder;

a calcium fluoride powder; and

a molybdenum disulfide powder;

These powers are added and mixed to produce a mixed powder having the composition according to any one of the above (1) to (17). The resulting mixed powder is subjected to compacting to obtain a compressed powder, and the compressed powder is sintered at a temperature higher than a usual sintering temperature in the range of 700 to 950° C.

The obtained sintered material is gradually cooled at a cooling rate of from 5 to 10° C./min, slower than a known cooling rate of 15° C./min or faster.

A Cu—Ni—Sn copper-based sintered alloy exhibiting excellent friction properties and wear resistance is obtained in this manner. In the alloy, pores are dispersed and distributed in a matrix at a porosity of 5 to 25%.

The above-mentioned sintering temperature is preferably in the range of 900 to 1080° C., and more preferably in the range of 900 to 980° C.

FIGS. 6A and 6B are a plan view and a cross-sectional view, respectively, showing examples of the embodiment of a bearing made of a Cu—Ni—Sn copper-based sintered alloy which has excellent friction properties and wear resistance.

Next, the reasons the composition of the Cu—Ni—Sn copper-based sintered alloy according to the invention, which exhibits excellent friction properties and wear resistance, and x and y for the phase of the composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) are limited to the above will be described.

(A) Reason for Limitation on Composition

(a) Ni

Ni is a component for improving strength, friction properties and wear resistance under the high-temperature environment. However, when the content of Ni is less than 10%, a desired effect can not be obtained, and when the content of Ni is greater than 40%, resistance between a shaft and a sliding surface under the high-temperature environment increases, and thus the level of wear increases quickly. Accordingly, the content of Ni contained in the Cu—Ni—Sn copper-based sintered alloy according to the invention is set in the range of 10 to 40%.

(b) Sn

Sn is a component for forming a solid solution as the matrix with Cu and Ni to improve the strength and the wear resistance of a bearing. However, when the content of Sn is less than 5%, a desired strength-enhancing effect can not be obtained, and when the content of Sn is greater than 25%, wear and tear corresponding material such as a stainless steel shaft rapidly becomes greater, and the wear of the stainless steel is accelerated. Accordingly, the content of Sn is set in the range of 5 to 25%.

(c) P

P is a component for improving sinterability at the time of sintering and for improving the strength of a matrix, that is, the strength of a bearing. Accordingly, it is added as needed. However, when the content of P is less than 0.1%, unpreferably, sufficient strength can not be obtained, because sinterability is not sufficiently exhibited. In addition, when the content of P is greater than 0.9%, the strength of a sintered alloy is lowered, because the strength of a grain boundary portion is lowered quickly. Accordingly, the content of P is set in the range of 0.1 to 0.9%.

(d) C

C is a component existing as free graphite, the body of which is dispersed and distributed in a matrix. In addition, C is a component for improving the lubricating properties of a bearing and the wear resistance of a bearing and a stainless steel shaft. Accordingly, it is added as needed. However, when the content of C is less than 1%, a ratio of dispersion and distribution of free graphite is insufficient, and desired, excellent lubricating properties can not be ensured, and when the content of C is greater than 10%, the strength of a bearing is lowered quickly, and the wear thereof increases quickly. Accordingly, the content of C is set in the range of 1 to 10%.

(e) Calcium Fluoride

Calcium fluoride serves to significantly improve seizure resistance, and thus it is added as needed. However, when the content of calcium fluoride is less than 0.3%, a desired effect can not be obtained, and when the content of calcium fluoride is greater than 6%, strength, friction properties and wear resistance are lowered. Accordingly, the content of calcium fluoride is set in the range of 0.3 to 6%.

(f) Molybdenum Disulfide

Molybdenum disulfide serves to improve seizure resistance, and thus it is added as needed. However, when the content of molybdenum disulfide is less than 0.3%, a desired effect can not be obtained, and when the content of molybdenum disulfide is greater than 6%, strength, friction properties and wear resistance are lowered. Accordingly, the content of molybdenum disulfide is set in the range of 0.3 to 6%.

(B) Reason for Limitation on Phase of Cu_((4-x-y))Ni_(x)Sn_(y)

x and y for the phase of Cu_((4-x-y))Ni_(x)Sn_(y) are set in the range of 1.7 to 2.3 and in the range of 0.2 to 1.3, respectively. A CuNi₂Sn phase having a high hardness is largely generated on a matrix by sintering at a temperature in the range of 900 to 1080 degrees, which is higher than a normal temperature range, and by gradually cooling at a speed lower than a normal speed. However, a complete CuNi₂Sn phase is hardly generated, and a Cu_((4-x-y))Ni_(x)Sn_(y) phase in which x is in the range of 1.7 to 2.3 and y is in the range of 0.2 to 1.3 is generated. When x and y for a Cu_((4-x-y))Ni_(x)Sn_(y) phase is in these ranges, friction properties and wear resistance of the phase are improved.

First Example

The Cu—Ni—Sn copper-based sintered alloy according to the invention, which exhibits friction properties and wear resistance, will be described in detail with reference to the example. Powders having the following characteristics were provided as raw powders:

an atomized Cu—Ni powder having an average particle size of 150 μm or less, and having a composition containing 15 to 42.5% by mass of Ni and the remainder containing Cu and inevitable impurities;

a Cu—Ni—Sn alloy powder having an average particle size of 150 μm or less, and having a composition containing 25 to 60% by mass of Ni, 5 to 60% by mass of Sn and the remainder containing Cu and inevitable impurities;

an atomized Sn powder having an average particle size of 20 μm;

a Cu—P alloy (Cu-8.4% P eutectic alloy) powder having an average particle size of 150 μm or less;

a graphite powder having an average particle size of 20 μm;

a CaF₂ powder having an average particle size of 60 μm; and

a MoS₂ powder having an average particle size of 150 μm or less.

The raw powders added to obtain the final compositions described in Tables 1 and 2, a stearic acid of 1% was added thereto, and then the mixture was mixed in a V-shaped mixer for 20 minutes. Subsequently, the mixture was subjected to pressing to obtain a compressed powder, and the compressed powder was sintered at a predetermined temperature in the range of 900 to 1080° C. in an ammonia decomposed gas atmosphere. As a result, ring-shaped test pieces 1 to 16 of the Cu—Ni—Sn copper-based sintered alloy according to the invention, ring-shaped comparative pieces 1 to 8 of a Cu—Ni—Sn copper-based sintered alloy, and ring-shaped test pieces 1 to 3 of a known Cu—Ni—Sn copper-based sintered alloy, which respectively had the compositions and the porosities described in Tables 1 and 2, were prepared. These all had the same size as follows: outside diameter 18 mm×inside diameter 8 mm×height 8 mm.

A representative one of the obtained ring-shaped test pieces 1 to 16 of the Cu—Ni—Sn copper-based sintered alloy according to the invention was observed by EPMA, and the observed structure is shown in pattern diagrams 1 to 5. FIG. 1 is a pattern diagram showing a structure of a Cu—Ni—Sn copper-based sintered alloy 1 according to the invention, FIG. 2 is a pattern diagram showing a structure of the Cu—Ni—Sn copper-based sintered alloy 3 according to the invention, FIG. 3 is a pattern diagram showing a structure of the Cu—Ni—Sn copper-based sintered alloy 4 according to the invention, FIG. 4 is a pattern diagram showing a structure of the Cu—Ni—Sn copper-based sintered alloy 8 according to the invention, and FIG. 5 is a pattern diagram showing a structure of the Cu—Ni—Sn copper-based sintered alloy 16 according to the invention.

The obtained ring-shaped test pieces 1 to 16 of the Cu—Ni—Sn copper-based sintered alloy according to the invention, ring-shaped comparative pieces 1 to 8 of a Cu—Ni—Sn copper-based sintered alloy, and ring-shaped test pieces 1 to 3 of a known Cu—Ni—Sn copper-based sintered alloy were dipped in synthetic oil. Using the ring-shaped test pieces 1 to 16 of the Cu—Ni—Sn copper-based sintered alloy according to the invention, ring-shaped comparative pieces 1 to 8 of a Cu—Ni—Sn copper-based sintered alloy, and ring-shaped test pieces 1 to 3 of a known Cu—Ni—Sn copper-based sintered alloy, which had been dipped in the synthetic oil, the tests described below were performed.

Crush Test:

The ring-shaped test pieces 1 to 16 of the Cu—Ni—Sn copper-based sintered alloy according to the invention, ring-shaped comparative pieces 1 to 8 of a Cu—Ni—Sn copper-based sintered alloy, and ring-shaped test pieces 1 to 3 of a known Cu—Ni—Sn copper-based sintered alloy, which had been dipped in the synthetic oil, were heated to 120° C., and a load was applied to the heated ring-shaped test samples from the radial direction thereof. The crush loads at the time that the ring-shaped test pieces were crushed were measured, and the strength and toughness of each test piece were evaluated as described in Tables 1 and 2.

Wear Resistance Test:

A shaft made of SUS304 and finished with 6S was inserted to the ring-shaped test pieces 1 to 16 of the Cu—Ni—Sn copper-based sintered alloy according to the invention, ring-shaped comparative pieces 1 to 8 of a Cu—Ni—Sn copper-based sintered alloy, and ring-shaped test pieces 1 to 3 of a known Cu—Ni—Sn copper-based sintered alloy, which had been dipped in the synthetic oil. Then, the ring-shaped test pieces were heated to 120° C., while a load of 0.2 MPa was applied from the outside of the ring-shaped test pieces in the radial direction (the direction perpendicular to the axis direction of the shaft) of the ring-shaped test pieces 1 to 16 of the Cu—Ni—Sn copper-based sintered alloy according to the invention, ring-shaped comparative pieces 1 to 8 of a Cu—Ni—Sn copper-based sintered alloy, and ring-shaped test pieces 1 to 3 of a known Cu—Ni—Sn copper-based sintered alloy. Subsequently, the shaft was rotated at a rate of 50 n/min for 30 minutes. The maximum wear depth of the inside diameter of each test piece was measured, and the strength, friction properties, and wear resistance of each test piece were evaluated as described in Tables 1 and 2.

Seizure Resistance Test:

A shaft made of SUS304 and finished with 6S was inserted to the ring-shaped test pieces 1 to 16 of the Cu—Ni—Sn copper-based sintered alloy according to the invention, ring-shaped comparative pieces 1 to 8 of a Cu—Ni—Sn copper-based sintered alloy, and ring-shaped test pieces 1 to 3 of a known Cu—Ni—Sn copper-based sintered alloy, which had been dipped in the synthetic oil. Then, the ring-shaped test pieces 1 to 16 of the Cu—Ni—Sn copper-based sintered alloy according to the invention, ring-shaped comparative pieces 1 to 8 of a Cu—Ni—Sn copper-based sintered alloy, and ring-shaped test pieces 1 to 3 of a known Cu—Ni—Sn copper-based sintered alloy were maintained at 120° C., and the shaft was rotated at a rate of 50 n/min for 30 minutes, while a load was applied in the radial direction (the direction perpendicular to the axis direction of the shaft) of the ring-shaped test pieces. Subsequently, the load was gradually increased, and the load at the time that seizure was generated was measured. The seizure resistance of each test piece was evaluated as described in Tables 1 and 2.

TABLE 1 Cu—Ni—Sn copper- Cu_((4-x-y))Ni _(x) Sn _(y) Crush Maximum Seizure based sintered Composition (% by mass) phase load wear depth load alloy Ni Sn P C CaF₂ MoS₂ Cu x y Porosity (%) (MPa) (μm) (MPa) Examples 1 24.1 8.9 — — — — balance 1.9 1.1 11.4 422 3 4.2 of the 2 24.3 10.5 0.3 — — — balance 1.9 1.2 10.4 455 2 5.2 invention 3 25.0 11.1 — 6.4 — — balance 1.9 1.1 11.3 391 1 6.4 4 20.0 9.1 0.4 7.2 — — balance 1.8 1.1 10.1 408 1 6.4 5 28.0 11.2 — — 3.1 — balance 2.0 1.1 12.4 402 2 4.2 6 26.6 12.3 0.4 — 4.5 — balance 2.2 1.1 12.2 421 4 6.4 7 32.5 8.9 — 5.6 1.1 — balance 2.1 0.8 10.5 365 2 6.4 8 24.4 15.3 0.2 3.8 2.2 — balance 2.1 1.0 10.8 381 3 5.8 9 24.1 18.2 — — — 2.1 balance 2.1 1.2 11.3 411 1 6.1 10 23.2 13.2 0.2 — — 2.4 balance 2.1 1.1 10.5 420 1 5.2 11 25.3 14.4 — 5.1 — 2.5 balance 2.1 1.0 14.1 365 1 6.4 12 34.2 14.6 0.2 3.2 — 2.2 balance 2.2 0.9 12.3 381 2 6.4 13 34.5 12.1 — — 4.3 2.6 balance 2.2 0.8 12.2 392 3 4.9 14 32.0 13.1 0.3 — 2.1 2.2 balance 2.1 0.7 13.6 404 1 5.2 15 33.5 16.2 — 1.8 5.1 2.0 balance 2.1 0.7 13.2 374 2 5.6

TABLE 1 Cu—Ni—Sn copper- Cu_((4-x-y))Ni _(x) Sn _(y) Crush Maximum Seizure based sintered Composition (% by mass) phase load wear depth load alloy Ni Sn P C CaF₂ MoS₂ Cu X y Porosity (%) (MPa) (μm) (MPa) 16 33.3 16.1 0.2 1.6 3.8 2.9 balance 1.9 1.0 12.0 380 2 6.5 comparative 1 8.3 11.2 — — — — balance 1.6* 1.2 11.2 298 82 1.5 examples 2 48.3 10.0 — — — — balance 2.4* 0.8 10.3 320 58 2.1 3 25.0 4.2 — — — — balance 2.1 0.1* 11.6 310 63 1.5 4 24.2 28.2 — — — — balance 1.8 1.4* 13.1 365 71 2.6 5 8.1 10.5 0.2 — — — balance 1.6* 1.1 14.2 382 82 1.1 6 49.1 10.3 0.2 — — — balance 2.4* 1.1 10.8 371 105 1.4 7 24.0 4.1 — 3.1 — — balance 2.0 0.1* 12.1 280 65 2.8 8 24.6 28.4 — 3.3 — — balance 2.2 1.4* 12.5 315 89 3.2 known 1 24.1 8.1 0.2 — — — balance — 11.5 325 120 1.1 examples 2 24.3 7.8 — 3.1 — — balance — 11.3 354 63 1.4 3 23.8 7.8 — — — 2 balance — 11.2 341 95 1.3 *mark shows the value that is out of the conditions of the invention.

The Cu—Ni—Sn copper-based sintered alloy according to any one of the above (1) to (17), exhibits excellent friction properties and wear resistance. In addition, the alloy according to the invention exhibits improved friction properties and wear resistance when it is used for various electrical parts and mechanical parts, and particularly, for an oil-impregnated bearing. Particularly, when the alloy according to the invention is used for the bearing of a shaft having a high rotation speed, a bearing having a long lifetime is effectively obtained. 

1. A Cu—Ni—Sn copper-based sintered alloy comprising a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) is dispersed in a matrix of the Cu—Ni—Sn copper-based sintered alloy containing Ni, Sn, and Cu.
 2. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) is dispersed in a matrix.
 3. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) and a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3) are dispersed in a matrix.
 4. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 1 to 10% by mass of C and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) and a graphite phase are dispersed in a matrix.
 5. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 1 to 10% by mass of C and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3) and a graphite phase are dispersed in a matrix.
 6. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.3 to 6% by mass of calcium fluoride and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) and a calcium fluoride phase are dispersed in a matrix.
 7. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 0.3 to 6% by mass of calcium fluoride and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3) and a calcium fluoride phase are dispersed in a matrix.
 8. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 1 to 10% by mass of C, 0.3 to 6% by mass of calcium fluoride and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a graphite phase and a calcium fluoride phase are dispersed in a matrix.
 9. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 1 to 10% by mass of C, 0.3 to 6% by mass of calcium fluoride and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3), a graphite phase and a calcium fluoride phase are dispersed in a matrix.
 10. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3) and a molybdenum disulfide phase are dispersed in a matrix.
 11. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3) and a molybdenum disulfide phase are dispersed in a matrix.
 12. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 1 to 10% by mass of C, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a graphite phase and a molybdenum disulfide phase are dispersed in a matrix.
 13. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 1 to 10% by mass of C, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3), a graphite phase and a molybdenum disulfide phase are dispersed in a matrix.
 14. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.3 to 6% by mass of calcium fluoride, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a calcium fluoride phase and a molybdenum disulfide phase are dispersed in a matrix.
 15. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 0.3 to 6% by mass of calcium fluoride, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3), a calcium fluoride phase and a molybdenum disulfide phase are dispersed in a matrix.
 16. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 1 to 10% by mass of C, 0.3 to 6% by mass of calcium fluoride, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a graphite phase, a calcium fluoride phase and a molybdenum disulfide phase are dispersed in a matrix.
 17. A Cu—Ni—Sn copper-based sintered alloy comprising a composition containing 10 to 40% by mass of Ni, 5 to 25% by mass of Sn, 0.1 to 0.9% by mass of P, 1 to 10% by mass of C, 0.3 to 6% by mass of calcium fluoride, 0.3 to 6% by mass of molybdenum disulfide and the remainder containing Cu and inevitable impurities, and having a structure in which a phase of a composition containing Cu_((4-x-y))Ni_(x)Sn_(y) (where x: 1.7 to 2.3, y: 0.2 to 1.3), a phase of a composition containing Cu_((4-z))P_(z) (where z: 0.7 to 1.3), a graphite phase, a calcium fluoride phase and a molybdenum disulfide phase are dispersed in a matrix.
 18. A bearing which is made of the Cu—Ni—Sn copper-based sintered alloy according to claim
 1. 